[bug report] iwlwifi: mvm: use dev_coredumpsg()

[Dan Carpenter <dan.carpenter@xxxxxxxxxx>]

Hello Aviya Erenfeld,

The patch 7e62a699aafb: "iwlwifi: mvm: use dev_coredumpsg()" from Sep
20, 2016, leads to the following static checker warning:

	drivers/net/wireless/intel/iwlwifi/mvm/fw-dbg.c:821 iwl_mvm_fw_error_dump()
	error: we previously assumed 'fw_error_dump->trans_ptr' could be null (see line 809)

drivers/net/wireless/intel/iwlwifi/mvm/fw-dbg.c
   805  dump_trans_data:
   806          fw_error_dump->trans_ptr = iwl_trans_dump_data(mvm->trans,
   807                                                         mvm->fw_dump_trig);
   808          fw_error_dump->op_mode_len = file_len;
   809          if (fw_error_dump->trans_ptr)
   810                  file_len += fw_error_dump->trans_ptr->len;

We assume ->trans_ptr can be NULL.

   811          dump_file->file_len = cpu_to_le32(file_len);
   812  
   813          sg_dump_data = alloc_sgtable(file_len);

That probably means file_len is zero?  (didn't look).  That means
sg_dump_data is ZERO_SIZE_PTR (16).

   814          if (sg_dump_data) {
   815                  sg_pcopy_from_buffer(sg_dump_data,
   816                                       sg_nents(sg_dump_data),
   817                                       fw_error_dump->op_mode_ptr,
   818                                       fw_error_dump->op_mode_len, 0);
   819                  sg_pcopy_from_buffer(sg_dump_data,
   820                                       sg_nents(sg_dump_data),
   821                                       fw_error_dump->trans_ptr->data,

Leading to an oops.

   822                                       fw_error_dump->trans_ptr->len,
   823                                       fw_error_dump->op_mode_len);
   824                  dev_coredumpsg(mvm->trans->dev, sg_dump_data, file_len,
   825                                 GFP_KERNEL);
   826          }
   827          vfree(fw_error_dump->op_mode_ptr);
   828          vfree(fw_error_dump->trans_ptr);
   829          kfree(fw_error_dump);
   830  
   831  out:
   832          iwl_mvm_free_fw_dump_desc(mvm);
   833          mvm->fw_dump_trig = NULL;
   834          clear_bit(IWL_MVM_STATUS_DUMPING_FW_LOG, &mvm->status);
   835  }

regards,
dan carpenter